# gdb -q firefox 
Reading symbols from firefox...
Reading symbols from /usr/lib/debug//usr/bin/firefox.debug...
(gdb) set follow-fork-mode child
(gdb) run
Starting program: /usr/bin/firefox 
[Attaching after process 2896 fork to child process 2900]
[New inferior 2 (process 2900)]
[Detaching after fork from parent process 2896]
[Inferior 1 (process 2896) detached]
process 2900 is executing new program: /usr/lib/firefox/firefox
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/libthread_db.so.1".

Thread 2.1 "firefox" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0xb6ff9010 (LWP 2900)]
0x0040f4e4 in free ()
(gdb) bt
#0  0x0040f4e4 in free ()
#1  0xb6d1de0a in __GI__IO_setb (f=f@entry=0xb6901060, b=b@entry=0x0, eb=eb@entry=0x0, a=a@entry=0)
    at genops.c:349
#2  0xb6d1cd64 in _IO_new_file_close_it (fp=fp@entry=0xb6901060) at fileops.c:154
#3  0xb6d13e98 in _IO_new_fclose (fp=0xb6901060) at iofclose.c:53
#4  0x0040b2b0 in ?? ()
#5  0x00495fce in __libc_csu_init ()
#6  0xb6ce42e0 in __libc_start_main (main=0x40b624 <_start+452>, argc=1, argv=0xbefff4c4, 
    init=0x495fa1 <__libc_csu_init>, fini=0x495fe1 <__libc_csu_fini>, 
    rtld_fini=0xb6fe14cd <_dl_fini>, stack_end=0xbefff4c4) at libc-start.c:264
#7  0x0040b494 in _start ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb)